This invention relates to the field of detection apparatus, particularly for controlled or dangerous substances, and more particularly to chemical and explosive detection apparatus for screening persons or objects for the presence of trace amounts of target substances.
U.S. Federal Aviation Administration safety concerns for the traveling public, combined with increased boldness of terrorists, has led to a need to screen for trace quantities of substances upon a person or object, in addition to the current use of metal detectors and x-ray systems. Trace detection systems, rather than bulk detection systems, are of increasing interest to identify individuals who recently have handled explosives materials by detecting trace amounts or even vapors from particular substances. Practical requirements of a detection system include the need to operate quickly in order to screen a high volume of people, high reliability of equipment for repeated and high-volume use, high accuracy, and a quick cleaning cycle after detection of a controlled or dangerous substance. It also is important that the system not occupy an excessive amount of physical space and that it be a self-contained unit with easy installation and easy operation.
In the case of screening persons, a trace detection system must be relatively non-invasive, preferably involving no physical contact. A particulate collection and detection system that involves wiping or brushing a surface can improve test accuracy but can consume too much per-test time and can invade the physical privacy of the person being screened. Linker et al., U.S. Pat. No. 5,915,268 (1999), incorporated herein by reference, is an example of a vertical flow chemical detection portal. The U.S. Pat. No. 5,915,268 patent discloses a preferred design having two sides, two floor vents (effectively dividing the exhaust stream), two preconcentrators, and two detectors. The U.S. Pat. No. 5,915,268 patent teaches the use of a portal with each of the two sides having a top portion, a middle portion, and a bottom portion, where each portion is flat, and where the sides, along with a connecting transom, form a test space having a smaller cross-section at the bottom of the test space than at the top of the test space to partially maintain air flow velocities despite losses from an open entry side and exit from the test space. Air flow over an object picks up particles which are carried through either floor vent to a corresponding detector. The U.S. Pat. No. 5,915,268 patent does not teach the use of any means to increase sample particle collection, to contain collected particles, or to reduce washout (i.e., the reflection of air off an object in the test space causing air to wash out of open portal sides, thus reducing the number of particles in a collection sample).
Fritz, U.S. Pat. No. 6,058,929 (2000), is an example of an adjustable exhaust hood with an air curtain. The U.S. Pat. No. 6,058,929 patent teaches a varied exhaust airflow across an exhaust hood with an open underside and a grease filter, and an intake fan to create a partial air curtain to trap the flow of rising exhaust air, which is warm and laden with smoke and grease, within the exhaust hood. The U.S. Pat. No. 6,058,929 patent does not teach substance detection device having an air curtain for increased sample size.
Explosives chemicals commonly used by terrorists can have extremely low vapor pressure which can make explosives vapor detection difficult, especially in conjunction with a short screening time. Explosives detection is performed mainly by bomb-sniffing dogs, which can be time-consuming and can be physically intrusive and intimidating to people. Detection systems can use highly sensitive detectors in order to detect trace amounts of explosives chemicals. A collection system that does not account for sample losses due to washout can be limited in its probability of detection of trace amounts of explosives and controlled substances. An improved collection system, which does not lose a significant portion of a collection sample due to washout and which can concentrate the collection sample prior to detection analysis, can increase the probability of detection.
There is a need for a non-invasive, privacy-protecting, detection portal comprising a collection system that is capable of containing a collection sample of trace amounts of a substance, limiting sample losses due to washout, and collecting a larger number of sample particles in order to effectively increase the probability of detection.
This invention provides a portal apparatus suitable for screening a person or other object for the presence of trace amounts of a target substance substantially thereon. The portal apparatus comprises a portal comprising two facing sides and a transom, together forming a test space, where the two facing sides comprise substantially vertical walls, configured in a concave shape across a horizontal cross-section for reducing washout from an open entry side and/or an open exit side. The portal apparatus comprises a plurality of gas nozzles for dislodging particles of the target substance on the object and a plurality of ionizing spray devices for dislodging particles of the target substance by ionization. The portal apparatus further comprises an air curtain. In a preferred embodiment, the portal apparatus further consists of one-sided exhaust through a floor vent intake.
This invention provides a detection system suitable for screening a person or other object for the presence of trace amounts of a target substance substantially thereon. The detection system comprises a portal, a preconcentrator, a detector, and a collector subsystem comprising: an airflow device, gas nozzles for dislodging particles of the target substance on the object, and ionizing spray devices for dislodging particles by ionization. The portal can comprise two facing sides, where each side is substantially concave-shaped across a horizontal cross-section. In a preferred embodiment, the portal apparatus further consists of one-sided exhaust through a floor vent intake.